Yagi-type multiband antenna having one element parasitic in one frequency band and driven in another frequency band

ABSTRACT

A Yagi-type multiband antenna including a driven element, a director and a reflector as parasitic elements in which a feeder between one of the parasitic elements and the transmitter may be switched on for making this one parasitic element operable as driven element of a two-element antenna system.

United States Patent [72] Inventor Klaus Neumann 2,703,840 3/1955Carmichael 343/832 Am Klosterberg13,6 67 St., Ittgbert (Saar), 2,268,6401/1942 Brown 343/819 66mm 3.175.219 3/1965 Wernick et a1. 343/815 X [21]Appl. No. 693,381 3,176,298 3/1965 Nettles 343/722 Filed 1967 FOREIGNPATENTS [451 Paemed "M33197! 906,636 9/1962 Great Britain 343/749 OTHERREFERENCES [54] YAGl-TYPE MULTIBAND ANTENNA HAVING NE Mitchell, R. H.,Three-Band Interlaced Beams," CQ,

ELEMENT PARASITIC IN ONE FREQUENCY Nov., 1968, PP- 102- 103, 130, 148BAND AND DRIVEN lN ANOTHER FREQUENCY A.R.R.L., Compact 3-Band ParasiticBeam," The BAND A.R.R.L. Antenna Book, Chapt. 12, pp. 272- 274, TheAmer- 3 Claims, 1 Drawing Fig. ican Radio Relay League, lnc., 1960 [52]US. Cl 343/722, Primary Examiner-Herman Karl Saalbach 34 /72 3/8l5, 34 I43/8 2, 34 /376 Assislanl Examiner-Wm. H. Punter [51] Int. Cl H0lq21/12, Azmmey-John J. Dennemeyer "HOIq 21/30 [50] Field of Search343/722-730,

315-3 9 335-337 7 749-752, ABSTRACT: A Yagi-type multiband antennaincluding a 700 TV, 332 driven element, a director and a reflector asparasitic elements in which a feeder between one of the parasiticelements and [56] References Cited the transmitter may be switched onfor making this one UNITED STATES PATENTS parasitic element operable asdriven element of a two-element 2,640,933 6/1953 Spindler 343/832 x amenSystem- [6 12 9 DE 9 B 3 0 A OJZSX, 4

A -mzst, 5 1 /7 2 10 77 YAGI-TYPE MULTHBAND ANTENNA HAVING ONE ELEMENTPARASHTKC IN ONE FREQUENCY BAND AND DRIVEN TN ANOTHER FREQUENCY BAND Theinvention relates to a Yagi-type multiband antenna having at least twoparasitic elements for different resonance frequencies for which theresonance is customarily produced by inserting different wave trapsinside the elements. As a rule, one does not employ a greater numberthan three frequencies and these frequencies have a maximum magnitudeproportion of about 1:2. If one employs for example a three-elementantenna it would constitute only a compromise arrangement in relation toits antenna gain because the spacings between the elements can bedesigned at best only for one resonance frequency. This arrangement istherefore frequently improved by inserting a separate reflector for thehighest resonance frequency.

It is naturally also possible to provide additional driven elements. Forthis purpose the available length of the antenna boom is alwaysimportant and this in turn depends on the spacing reflector-director forthe lowest resonance frequency. This spacing is on the average about0.25-0.35 wavelength A.

It is an object of the invention to provide a Yagi-type multibandantenna having at least two parasitic elements without requiring anextension of the antenna boom and without additional driven elements tomake this antenna resonant for additional transmitted or receivedfrequencies. Accordingly it is proposed that at least one parasiticelement may be operated as driven element for an additional resonancefrequency associated with the distance between this particular elementand a second parasitic element while the feeder of the former drivenelement is disconnected. The invention makes use of an element spacingbetween parasitic elements which has not been used so far and providesthereby without extension of the antenna boom and without additionaldriven elements a new antenna system which is operated at the particularadditional resonance frequency for which the available element spacingpromises an optimum antenna gain.

Since the element spacing between two parasitic elements is usuallylarger than the distance from one of these elements to the drivenelement for the original frequencies, the additional resonance frequencywill in most instances be lower than the frequency for which themultiband antenna was originally designed. This is the case for examplewhen-starting from a three element antenna-the two outer parasiticelements may be operated as a two-element antenna. Thus especially for afrequency which is lower by a harmonic interval than the lowestfrequency of the three element arrangement with a 0.25 parasitic elementspacing, a combination driven element-director with about 0.125 A offersan optimum gain. One should choose a two-element arrangement as drivenelementreflector as soon as this distance lies-between 0.15 to 0.2 A.

It will be understood that the elements used for a two-elementarrangement are made resonant for the additional lower resonancefrequency. This is accomplished in the simplest manner by an actual oran electrical extension of the elements with the addition of new wavetraps for the lowest resonance frequency of the three elementarrangement, but there are also other equivalent means which come withinthe scope of this invention.

it is also important to make sure that the parasitic element which isused as driven element in the two-element arrangement and which isappropriately fed over a y-rnatch, is not damped or detuned by matchingdevices or the like in its function as reflector or director for theother frequencies of the three-element arrangement due to the feeder.The feeder of the parasitic element which is inserted as driven eiementaccording to the invention, is therefore appropriately designed for ashort-circuiting at the feed point, which is also true for a parasiticelement, which is split for feeding purposes,

The objects and advantages of the multiband antenna according to theinvention will become more apparent from the following detaileddescription in combination with the accompanying drawing showing anembodiment of the invention for purposes of illustration.

in the drawing the invention is illustrated on the basis of athree-element antenna. The three elements consist of the driven element1 having a driven element length S,,,, of the reflector 2 having areflector length R and of the director 3 having a director length D,,,.The element spacings A are 0.125 A. The three elements are fixed to ahorizontal antenna boom 4 so that the direction of the main lobe is inthe direction of arrow B.

The three-element multiband antenna is assumed to be tuned for the 20mamateur band for a resonance frequency of l4l50 kHz. Normally the threeelements are made resonant for additional frequencies by inserting wavetraps in the illuswave traps. In the interest of a tion these additionalwave traps are not illustrated and the three-element antenna shown isresonant only for the given frequency.

According to the invention the large spacing A between the reflector 2and the director 3 is employed to obtain an additional lower resonancefrequency equivalent A2 without requiring an extension of the antennaboom 4. For this purpose one of the parasitic elements 2 and 3, in theembodiment shown the reflector 2, is employed as a driving element inthat a coaxial feeder 6 is connected to it for the lower frequency andthis is done most appropriately over the illustrate -y-match since thereflector 2 is normally a straight through pipe. To prevent that thisadditional feeder has harmful effects for the normal three elementoperation this feeder may be short-circuited by means of a switch 7 inthe feed point.

During normal operation the feeder 5 leading to the driving element 1 isconnected through a changeover switch 13 to the transmitter 14. in theother switch position the transmitter 14 operates on the parasiticelement 2 with a frequency which offers for the fixed spacing A to theother parasitic element 3 an optimum gain.

In the two-element operation according to the invention employing thereflector 2 as driving element the director 3 becomes the director. Thedriving element 1 does not interfere because it is out of resonance. Forthe additional frequency of the two-element operation the spacings R andD of the two elements 2 and 3 are not resonant. The new frequency isderived from the element spacing A when this spacing is equated with thevalue 0.125 72 which is favorable for a driving element-director system.In the illustrated example an additional lower resonance frequency ofabout 7075 kHz. is ob tained for which the thus obtained driving element2 as well as the director 3 must be made resonant by extensions to thedimensions 8,, and D respectively. To provide this severalpossibilities'exist. The simplest one is to bring the element lengths tothe resonance lengths S and D respectively by insertion of wave traps 8for the element 3 and wave traps 10 for the element 2. In this casethese elements would have to become approximately twice as long as theoriginal length D and R for the basic three-element configuration forthe 20 meter band. For this reason it seams appropriate for mechanicalreasons to electrically extend at least in part the element length forthe two element operation by inductance coils 9 and 1! respectively.

it is obvious that the two element arrangement for 7075 kHz. or the40m-band can be made resonant for additional adjacent frequency rangesby inserting additional wave traps or by equivalent means.

What is claimed is:

l. A Yagi-type multiband antenna comprising at least two parasiticelements and one driven clement adapted to operate at one resonancefrequency. and an electrical switch, at least one of said parasiticelements being controlled by said switch for operation in one switchcondition as a parasitic element at said one resonance frequency and foroperation in the other switch condition as a driven element at anadditional resonance frequency. the fixed spacing between the drivableparasitic element and at least one remaining parasitic element beingsuch as to effect optimum antenna gain at said additional resonancefrequency.

2. A Yagi-type multiband antenna comprising:

A. first and second parasitic elements each tuned for differentresonance frequencies,

B. one driven element, said first parasitic element being parasitic atone frequency and in addition being operable as a driven element at asecond frequency, and

C. switching means selectively operable to make electrical connectionsto the three elements to connect said driven element and said first andsecond parasitic elements to act as a three-element antenna at oneresonant frequency or alternatively to connect said first parasiticelement for operation as a driven element to form, in cooperation withthe second said parasitic element. a two-element antenna at a secondresonant frequency. said first parasitic element being of such lengthand construction as to reflect and reinforce the wave radiated by theone driven element without substantially changing the phase of theradiated wave 3. A Yagi-type multiband antenna according to claim 2,wherein the feeder leading to said drivable parasitic element may beshort circuited in the feed point.

t i i i

1. A Yagi-type multiband antenna comprising at least two parasiticelements and one driven element adapted to operate at one resonancefrequency, and an electrical switch, at least one of said parasiticelements being controlled by said switch for operation in one switchcondition as a parasitic element at said one resonance frequency and foroperation in the other switch condition as a driven element at anadditional resonance frequency, the fixed spacing between the drivableparasitic element and at least one remaining parasitic element beingsuch as to effect optimum antenna gain at said additional resonancefrequency.
 2. A Yagi-type multiband antenna comprising: A. first andsecond parasitic elements each tuned for different resonancefrequencies, B. one driven element, said first parasitic element beingparasitic at one frequency and in addition being operable as a drivenelement at a second frequency, and C. switching means selectivelyoperable to make electrical connections to the three elements to connectsaid driven element and said first and second parasitic elements to actas a three-element antenna at one resonant frequency or alternatively toconnect said first parasitic element for operation as a driven elementto form, in cooperation with the second said parasitic element, atwo-element antenna at a second resonant frequency, said first parasiticelement being of such length and construction as to reflect andreinforce the wave radiated by the one driven element withoutsubstantially changing the phase of the radiated wave.
 3. A Yagi-typemultiband antenna according to claim 2, wherein the feeder leading tosaid drivable parasitic element may be short-circuited in the feedpoint.